Why do Christians believe in the necessity of holiness?

Christians believe in the necessity of holiness because it is directly tied to the nature of God, who is holy. In the sermon, it is emphasized that God's holiness defines all His attributes, including love and mercy. In Leviticus, God commands His people to be holy because He is holy. This call to holiness signifies a separation from sin and a dedication to living according to God's standards. Holiness is not merely a behavioral modification but originates from the believer's identity in Christ. As Christians are made new creations, they are called to reflect Christ's righteousness in their lives, pursuing holiness as an expression of their gratitude for God's grace.